In general, a receiving apparatus (a radio receiver) which receives a radio broadcast wave (e.g., an AM broadcast wave and an FM broadcast wave) is mounted in a moving object, such as a vehicle. In such a vehicle-mounted receiving apparatus, because the surrounding environment of the moving object varies from moment to moment according to the movement of the moving object, there occurs a situation in which the vehicle-mounted receiving apparatus cannot receive a radio broadcast excellently while receiving the radio broadcast because of noise mixed into the radio broadcast, the noise resulting from a change in the received field strength, neighboring interference, multipath interference, and so on.
In order to avoid the occurrence of such a situation, a vehicle-mounted radio receiver reduces the noise by performing functions, such as so-called high cut control (High Cut Control), stereo blend control (Stereo Blend Control) and softmute control (Softmute Control).
For example, there has been provided a vehicle-mounted radio receiver which, in order to implement an appropriate operating state irrespective of the presence or absence of an adjacent station, detects an adjacent station having a carrier frequency adjacent to the reception frequency by using an adjacent station detector, and, when detecting such an adjacent station, changes the control of input/output characteristics, such as a channel separation characteristic, a blend characteristic, a high cut characteristic, and a softmute characteristic (for example, see patent reference 1).
[Patent reference 1] JP,2005-5819,A (pp. 5 to 9 and FIGS. 1 to 13)
Because conventional receiving apparatuses are constructed as mentioned above, if noise which disables them to detect the received field strength, the neighboring interference, and the multipath interference is mixed, the high cut control does not work and, as a result, the noise cannot be cut and therefore the audibility is impaired. For example, because the neighboring interference becomes low inevitably when the received field strength is high (medium field strength or high field strength), it is determined whether to perform the high cut control according to the multipath interference, and, when the received field strength is high, the high cut control becomes difficult to run and therefore it becomes impossible to cut the noise excellently.
A further problem is that when the received field strength is high and the multipath interference is low, the high cut control does not run even in a state in which stereo demodulation cannot be performed excellently, and, as a result, mixing of noise occurs and the audibility is impaired.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a receiving apparatus which carries out noise cut excellently according to the state of the stereo demodulation irrespective of the neighboring interference and the multipath interference without impairing the audibility.